1. Field of the Invention
This invention pertains generally to medical devices and, more particularly, to a device for obtaining a sample from the intestinal tract of a person.
2. Description of Related Art
Heretofore, there have been some attempts to obtain samples from the intestinal tracts of human beings by means of relatively small capsules which are swallowed, then opened to collect a sample as they pass through the intestinal tract. Such devices are particularly useful in the small intestine where it is otherwise difficult to obtain samples for chemical and microbiological analysis.
One example of a swallowable capsule for obtaining samples of gastric and/or intestinal fluids is found in U.S. Pat. No. 4,481,952. That capsule has an inner chamber with an inlet port which is normally sealed off by a film or coating which is dissolved by the fluids in the portion of the body from which the sample is to be obtained. The capsule also has a spring-actuated closure which is held in an open position relative to the port by a restraint fabricated of a material which is dissolved by the sampled fluid. Thus, the capsule is intended to open when it reaches the area in which the sample is to be taken, then close after the sample is obtained to contain the sample and protect it from contamination as capsule continues its passage through other parts of the body. One problem with this type of device is that it does not provide very precise control over the closing of the capsule, with the result that the sample may be lost or become contaminated before the closing occurs.
U.S. Pat. No. 4,239,040 discloses a capsule for discharging drugs into or collecting samples from the body, which utilizes a meltable thread to hold a pistonlike element against the force of a spring. Movement of the piston-like element serves to push drugs out of or draw a sample into the capsule, and the thread is melted by a heater which is energized by a an electric circuit including a tunable receiver which responds to an externally transmitted electric signal.
U.S. Pat. Nos. 4,439,197 and 4,507,115 shows capsules for discharging medicine or obtaining samples, utilizing shape memory elements to move piston-like elements in response to temperature changes. In the '197 patent, the capsule contains a power source, a switching circuit, and a radio receiver which respond to radio frequency signals to control the temperature of the shape memory element, and in the '115 patent, the shape memory element is heated ultrasonically.